<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        //    检测是否是数字，包括整数，小数
        while (true) {
            const a = prompt("请输入一个字符")
            const reg = /^\d+|(\.\d+)?$ /

            if (reg.test(a)) {
                alert(`${a}是数字`)
            } else {
                alert(`${a}不是数字`)
            }
        }



    </script>

</body>

</html>